• Korean Journal of Metals and Materials
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• v.49 no.3
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• pp.237-242
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• 2011

The effect of shearing speed on the shear force and energy of Sn-0Ag-0.5Cu solder ball was investigated. Various UBM (under bump metallurgy)'s on Cu pads were used such as ENEPIG (Electroless Nickel, Electroless Palladium, Immersion Gold; Ni/Pd/Au), ENIG (Electroless Nickel, Immersion Gold; Ni/Au), OSP (Organic Solderability Preservative). To fabricate a shear test specimen, a solder ball, $300{\mu}m$ in diameter, was soldered on a pad of FR4 PCB (printed circuit board) by a reflow soldering machine at $245^{\circ}C$. The solder bump on the PCB was shear tested by changing the shearing speed from 0.01 m/s to 3.0 m/s. As experimental results, the shear force increased with a shearing speed of up to 0.6 m/s for the ENIG and the OSP pads, and up to 0 m/s for the ENEPIG pad. The shear energy increased with a shearing speed up to 0.3 m/s for the ENIG and the OSP pads, and up to 0.6 m/s for the ENEPIG pad. With a high shear speed of over 0 m/s, the ENEPIG showed a higher shear force and energy than those of the ENIG and OSP. The fracture surfaces of the shear tested specimens were analyzed, and the fracture modes were found to have closer relationship with the shear energy than the shear force.

• Korean Journal of Metals and Materials
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• v.47 no.9
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• pp.580-585
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• 2009

The effects of shear speed and tip height on the high speed shear test of Sn-3.0wt.%Ag-0.5wt.%Cu ball joints were investigated. Solder balls of $450{\mu}m$ in diameter were reflowed at $245^{\circ}C$ on a FR4 PCB (Printed Circuit Board) in order to obtain a sample for the high-speed shear test. The UBM was comprised of Cu/Ni/Au, and the shear speed and tip height varied from 0.5 to 3.0 m/s, and from 10 to $135{\mu}m$, respectively. According to the experimental results, faster shear speed enhanced the shear strength of the solder joints, regardless of the tip height. The fraction of ductile (solder) fracture decreased when the shearing speed was raised from 0.5 to 3.0 m/s. With an increasing tip height from 10 to 50 and $135{\mu}m$, the fracture mode changed from pad lift to mixed (ductile and brittle) and ductile fracture, respectively, while the shearing energy also increased in the same order. The shear energy had a proportional relationship with the fraction of the solder fracture.

• Korean Journal of Metals and Materials
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• v.47 no.12
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• pp.842-851
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• 2009

The long-term reliability of Sn-0.3wt%Ag-0.7wt%Cu solder joints was evaluated and compared with Sn-3.0wt%Ag-0.5wt%Cu under thermal shock conditions. Test vehicles were prepared to use Sn-0.3Ag-0.7Cu and Sn-3.0Ag-0.5Cu solder alloys. To compare the shear strength of the solder joints, 0603, 1005, 1608, 2012, 3216 and 4232 multi-layer ceramic chip capacitors were used. A reflow soldering process was utilized in the preparation of the test vehicles involving a FR-4 material-based printed circuit board (PCB). To compare the shear strength degradation following the thermal shock cycles, a thermal shock test was conducted up to 2,000 cycles at temperatures ranging from $-40^{\circ}C$ to $85^{\circ}C$, with a dwell time of 30 min at each temperature. The shear strength of the solder joints of the chip capacitors was measured at every 500 cycles in each case. The intermetallic compounds (IMCs) of the solder joint interfaces werealso analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results showed that the reliability of Sn-0.3Ag-0.7Cu solder joints was very close to that of Sn-3.0Ag-0.5Cu. Consequently, it was confirmed that Sn-0.3Ag-0.7Cu solder alloy with a low silver content can be replaced with Sn-3.0Ag-0.5Cu.

• Journal of Technologic Dentistry
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• v.42 no.4
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• pp.321-325
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• 2020

Purpose: This study is to evaluate the accuracy of gypsum replica models made from various gypsum products. Methods: One main model was made of stainless steel by CNC milling process. Molds were formed from the main model, and the gypsum replica models were made using 8 types of type IV gypsum, 10 pieces each. The main model was digitized by a contact scanner (Incise; Renishaw) and the gypsum replicas were digitized by an optical scanner (E4; 3Shape A/S). The difference between the main model and the gypsum replicas were measured by inspection software (3D Systems). One-way ANOVA was performed to evaluate the statistical significance of differences between groups. In addition, the independent sample T test was performed to determine the difference between the conventional and scannable stone group (n=10, α=0.05). Results: The root mean square of the stone models were 7.24 ㎛ to 10.78 ㎛, and statistical significance was found between the two groups (SR, FR) and the other 6 groups (IS, SG, CA, CS, ER, EBG) (p<0.05). The accuracy of the gypsum replicas was 9.04 ㎛ and 7.62 ㎛ in the conventional and scannable stone group, respectively. There was statistical significance between the two groups (p<0.01). Conclusion: In the limited results of this study, the product with low setting expansion and the scannable showed high accuracy. Therefore, in order to obtain a stable and accurate scan model, it is more effective in terms of accuracy to use a scannable stone with a low setting expansion.

• The Korea Journal of Herbology
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• v.28 no.2
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• pp.9-15
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• 2013

Objectives : The root of Codonopsis pilosula (Fr.) Nannf. (Codonopsis Pilosulae Radix) has been traditionally used as a oriental medicine with an anti-thrombotic, antidiabetic, anticancer, and anti-gastric ulcer effects and immunological adjuvant. In this study, we investigated the effect of 70% ethanol extract of Codonopsis Pilosulae Radix (CPR-E) on ovalbumin (OVA)-induced allergic responses in mice. Methods : Mice were sensitized (1, 8, and 15 days) with OVA and airway challenged(22, 24, 26, 28, and 30 days) to induced allergic responses. CPR-E extract at doses of 50 and 100 mg/kg/body weight was orally administered from days 21 to 30 consecutively. The levels of allergic mediators such as histamine, OVA-specific immunoglobulin (Ig) E, and Th1/Th2 cytokines such as IFN-${\gamma}$ and IL-4 were measured in the sera of mice by ELISA. The histological change of lung tissue was observed by hematoxylin and eosin (H&E) staining. Results : CPR-E extract significantly decreased the serum levels of histamine, OVA-specific IgE, and IL-4 compared with those of OVA control group, but significantly increased the serum level of IFN-${\gamma}$. Based on H&E staining, CPR-E extract inhibited the infiltration of inflammatory cells into lung tissues with histological changes. Conclusions : These results indicate that CPR-E extract has anti-inflammatory and anti-allergic responses through regulating the cytokine balance, suggesting that the extract may be useful for the treatment of allergic inflammatory diseases such as bronchial asthma and allergic rhinitis.

• The Korea Journal of Herbology
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• v.28 no.2
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• pp.55-60
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• 2013

Objectives : Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by eczematous inflammtion of the skin. The chestnut inner shell extracts (CI) has been used as a cosmetic material for a long time in Korea. However, the precise anti-allergy effects of CI have yet to be clearly elucidated. In this study, we attempted to evaluate the effect of CI on mast cell-mediated allergy inflammation. Methods : To find the anti-allergy and inflammatory effect of CI, we investigated the inhibitory effect of CI on the production of inflammatory mediators using by enzyme-linked immunosorbent assay in phorbol 12-myristate 13-acetate (PMA) plus calcium ionophore (A23187) stimulated-human mast cell (HMC-1). Results : In this study, we found that CI did not show cytotoxic effect at up to 10 ug/ml on HMC-1. CI inhibited the production of tumor necrosis factor (TNF)-${\alpha}$, interleukin (IL)-6 and IL-8 in stimulated HMC-1. Maximal rate of TNF-${\alpha}$, IL-6 and IL-8 inhibition by CI (10 ug/ml) were about 47.6%, 44.1% and 22.5% respectively. In addition, we showed that Fr.3 isolated from n-Butyl alcohol layer of CI attenuated the production of TNF-${\alpha}$, IL-6 and IL-8 in HMC-1. Conclusion : Taken together, the findings of this study provide us with a novel insight action of CI as a potential molecule for use in the treatment of allergic inflammation diseases.

• International Journal of Computer Science & Network Security
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• v.22 no.12
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• pp.245-251
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• 2022

In this paper, a high gain, broadband planar vivaldi antenna (PVA) by utilizing a broadband stripline feed is developed for wireless communication for IoT systems. The suggested antenna is designed by attaching a tapered-slot construction to a typical vivaldi antenna, which improves the antenna's radiation properties. The PVA is constructed on a low-cost FR4 substrate. The dimensions of the patch are 1.886λ₀×1.42λ₀×0.026λ₀, dielectric constant Ɛ_r=4.4, and loss tangent δ=0.02. The width of the feed line is reduced to improve the impedance bandwidth of the antenna. The computed reflection coefficient findings show that the suggested antenna has a 46.2% wider relative bandwidth calculated at a 10 dB return loss. At the resonance frequencies of 6.5 GHz, the studied results show an optimal gain of 5.82 dBi and 85% optimal radiation efficiency at the operable band. The optometric analysis of the proposed structure shows that the proposed antenna can achieve wide enough bandwidth at the desired frequency and hence make the designed antenna appropriate to work in satellite communication and medical internet of things (M-IoT) healthcare applications.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.46 no.1
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• pp.55-67
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• 2023

Lightweight face recognition models, as one of the most popular and long-standing topics in the field of computer vision, has achieved vigorous development and has been widely used in many real-world applications due to fewer number of parameters, lower floating-point operations, and smaller model size. However, few surveys reviewed lightweight models and reimplemented these lightweight models by using the same calculating resource and training dataset. In this survey article, we present a comprehensive review about the recent research advances on the end-to-end efficient lightweight face recognition models and reimplement several of the most popular models. To start with, we introduce the overview of face recognition with lightweight models. Then, based on the construction of models, we categorize the lightweight models into: (1) artificially designing lightweight FR models, (2) pruned models to face recognition, (3) efficient automatic neural network architecture design based on neural architecture searching, (4) Knowledge distillation and (5) low-rank decomposition. As an example, we also introduce the SqueezeFaceNet and EfficientFaceNet by pruning SqueezeNet and EfficientNet. Additionally, we reimplement and present a detailed performance comparison of different lightweight models on the nine different test benchmarks. At last, the challenges and future works are provided. There are three main contributions in our survey: firstly, the categorized lightweight models can be conveniently identified so that we can explore new lightweight models for face recognition; secondly, the comprehensive performance comparisons are carried out so that ones can choose models when a state-of-the-art end-to-end face recognition system is deployed on mobile devices; thirdly, the challenges and future trends are stated to inspire our future works.

• Proceedings of the National Institute of Ecology of the Republic of Korea
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• v.4 no.4
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• pp.159-176
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• 2023

The conservation of the raccoon dog (Nyctereutes procyonoides) in South Korea requires the protection and preservation of natural habitats while additionally ensuring coexistence with human activities. Applying habitat map modeling techniques provides information regarding the distributional patterns of raccoon dogs and assists in the development of future conservation strategies. The purpose of this study is to generate potential habitat distribution maps for the raccoon dog in South Korea using geospatial technology-based models. These models include the frequency ratio (FR) as a bivariate statistical approach, the group method of data handling (GMDH) as a machine learning algorithm, and convolutional neural network (CNN) and long short-term memory (LSTM) as deep learning algorithms. Moreover, the imperialist competitive algorithm (ICA) is used to fine-tune the hyperparameters of the machine learning and deep learning models. Moreover, there are 14 habitat characteristics used for developing the models: elevation, slope, valley depth, topographic wetness index, terrain roughness index, slope height, surface area, slope length and steepness factor (LS factor), normalized difference vegetation index, normalized difference water index, distance to drainage, distance to roads, drainage density, and morphometric features. The accuracy of prediction is evaluated using the area under the receiver operating characteristic curve. The results indicate comparable performances of all models. However, the CNN demonstrates superior capacity for prediction, achieving accuracies of 76.3% and 75.7% for the training and validation processes, respectively. The maps of potential habitat distribution are generated for five different levels of potentiality: very low, low, moderate, high, and very high.

• The Journal of Economics, Marketing and Management
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• v.12 no.2
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• pp.73-81
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• 2024

Purpose: South Korea is a close ally of the US and an important partner of China. Caught between the two most powerful countries, South Korea's strategic directions are critical. This article emphasizes that the deeper core of the US-China trade war is to improve the business environment to attract foreign direct investment (FDI) to boost the economy, rather than engaging in the trade war. Research design, data, and methodology: Considering the complexity of this issue, this article applies a systematic analytical tool, the ABCD (Agility, Benchmarking, Convergence, and Dedication) model, to provide strategic guidance for inducing investments into South Korea in the context of the ongoing US-China trade war. Results: Specifically, South Korea needs to provide a more attractive business environment along the four points: expedite commercial activities through deregulation (Agility); adopt global standards of the flexible labor markets and technological developments (Benchmarking); integrate various industries and connect them to global value chains (Convergence); and create more economy-friendly policies rather than politics-oriented ones such as protectionism (Dedication). Conclusion: This study stands out not just by utilizing the ABCD model but, also by providing more systematic analysis and practical implications, particularly within the context of the escalating US-China competition. Unlike many existing studies that analyze the broader impacts of this geopolitical rivalry, this research delves into specific strategic guidelines for South Korea to attract FDI. The findings also provide implications for multinational corporations (MNCs) in choosing the locations for their overseas operations, particularly in South Korea.